1. Field of the Invention
The present invention relates to a compact image taking lens which has a high optical performance and is formed of two lenses and suitable for a compact imaging apparatus, an optical sensor, a module camera of a mobile phone, a web camera, and so on which use a solid-state imaging device such as a high resolution CCD or CMOS.
2. Description of the Related Art
In recent years, various kinds of imaging apparatuses using a solid-state imaging device such as a CCD or a CMOS are widely spread. Following miniaturization and improvement in performance of the imaging device, a compact and lightweight image taking lens having a high optical performance is required. Many studies have been done to provide an image taking lens satisfying both miniaturization and high optical performance. As the performance of the solid-state imaging device such as a CCD increases, an image taking lens even smaller in size and higher in optical performance is now required. In order to downsize the image taking lens, it is advantageous to reduce the number of lenses forming the image taking lens. However, in order to obtain a higher optical performance, it is advantageous to increase the number of lenses because it makes it easier to appropriately correct various aberrations and obtain an image taking lens having a high optical performance. Considering these, there has been proposed an image taking lens which is formed of two lenses and achieves a good balance between downsizing and optical performance.
Japanese Laid-open Patent Publications 2005-121685 and 2006-350275 each disclose a conventional image taking lens comprising, in order from an object side, a first lens having a positive power and a meniscus shape with a convex surface facing an object, and a second lens having a positive power and biconvex surfaces. In such conventional image taking lenses, the first lens has a large center thickness and a large radius of curvature on both the object side and the image side. Thus, the entire image taking lens is likely to have a relatively long focal length, and it may be difficult to sufficiently reduce its size and correct aberrations. Note that here the power of the lens is given by the inverse of the focal length.